Not that this post is really that helpful but I’m running Windows 7 on three boxes with FF 3.5 and haven’t experienced the issues you are having. My brother is running it on 3 machines as well and hasn’t reported crashing and hangups and he’s the type that would complain to me about it. We are all running Windows 7 Ultimate but I wouldn’t think the flavor of 7 would make the difference.
I have two home premiums @ home and one pro @ work. I am the IT admin here @ work. I can’t really say either way what is causing the crashes. Couple times a day... Strange. I just keep plugging away. No worries.